Tuesday, October 26, 2010

How does one go about discovering a particle so small that nobody can see it? The British physicist J.J. Thomson won the Nobel prize in 1906 for doing just that—discovering the electron. At Cambridge University, Thomson was the epitome of an absentminded professor, sporting a tweed jacket, round-rimmed spectacles, mustache and dishevelled hair.

While exploring the nature of cathode rays, he discovered that he could deflect their path with an electric field. Measuring the amount of deflection under various strength fields, he was able to determine the mass of these particles, which he found to be about 1,800 times lighter than the hydrogen atom.

He called these particles “corpuscles,” and (incorrectly) suggested that they make up all of the matter in atoms. Most scientists at the time believed that the atom was the most fundamental unit of matter and indivisible, so to them this was a shocking concept.

The "plum pudding" model of the atom

Thompson proposed a “plum pudding” model for the atom, in which thousands of tiny, negatively charged corpuscles move about inside a massless cloud of positive charge. This theory was disproved by a former student of Thomson, Ernest Rutherford. By examining how alpha particles scattered after colliding with a thin sheet of gold foil, Rutherford found that the atom must have a small core, or nucleus. Rutherford proposed that the atom might resemble a tiny solar system, with a massive, positively-charged center orbited by electrons.

Rutherford's gold foil experiment

Luckily the name corpuscles did not stick or else today we would be going to corpuscular stores like Radio Shack, or reading c-mail instead of e-mail. Eventually the word electron gained favor. It comes from the Greek word for amber, which was known for its ability to electrostatically attract small objects when rubbed with fur.

Monday, October 18, 2010

Hidden away in a rugged and remote corner of eastern Utah lies one of the most unique archeological sites in North America—Range Creek Canyon. Native Americans known as the Fremonts lived there for several hundred years up until about 1,300 AD when their way of life came to a sudden and mysterious end. Similar to the Anasazi, the Fremonts were ancestors of today’s Pueblo peoples.

The site remains largely untouched today thanks to Waldo Wilcox. He is the rancher that owned the land and protected this secret for 50 years until he eventually sold it to the state of Utah in 2001. Currently, the land is under the care of the University of Utah’s Archeology Department.

A stone and adobe granary

The Fremonts hunted and farmed. They grew corn and stored it in stone and adobe granaries that they built in out-of-the-way cliff sides. Over 38 have been identified so far. These granaries are at many different elevations and often located in extremely precarious spots. It is thought that in lean years they stored their corn in higher, more difficult to reach areas in order to protect their limited food supply.

A Fremont petroglyph

They were also prolific artists, creating many carvings into the cliff walls (know as petroglyphs) and paintings in caves and on rocks (known as pictograms). Their cave dwellings were well crafted and a rich source of artifacts: pottery, stone tools, arrowheads and other items. This unique find will no doubt be carefully studied for years to come and promises to reveal many details of their lives.

1) True of false: Ranch Creek Canyon was home to the Fremont people a thousand years ago.

2) The Fremonts relied on the farming of ______________ which they stored in stone and adobe ______________________.

Sunday, October 10, 2010

NASA called Apollo 15 the most successful manned space flight ever achieved. It was the first moon mission to use the Lunar Rover which allowed the crew to travel greater distances from the Lunar Module than ever before, even though for safety sake they avoided traveling farther than they could safely walk back in case the rover broke down. They also collected 170 lbs. of moon rocks, one of them being the Genesis Rock. When later examined by geologists it was found to be 4.5 billion years old—meaning it was formed shortly after the creation of the solar system.

Genesis Rock

One of the experiments carried out during Apollo 15’s moon landing—called the hammer and feather drop—was done as a bit of theater to test the original Galileo theory that objects of different mass will fall at the same rate in a vacuum. In it, we see Mission Commander David Scott drop a hammer and feather at the same time form the same height to see if they both hit the ground at the same time. Since the moon has no atmosphere, it was the perfect place to carry out the experiment.

Hard to believe, but a significant portion of the population still does not believe that the Apollo landings really took place—that they were staged by NASA. One poll of 18 to 25 year old American revealed that 25 percent of them were not sure that the landings actually happened.As we have discussed before, one exception is all it takes to disprove a theory and I should think the hammer and feather drop would be enough to dispel this myth. But then again, some people still think Elvis is alive.
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Sunday, October 3, 2010

How ironic that the heaviest naturally-occurring element, plutonium, was named after the dwarf planet Pluto. Plutonium was discovered in 1940 by Glenn Seaborg and his team at Berkeley University. His research became part of the top-secret Manhattan Project, so its discovery would not be made public until after the atomic bomb called Fat Man was dropped on Nagasaki to end World War II. Seaborg would receive the Nobel Prize in Chemistry in 1951 for the discovery of the transuranium elements, including: plutonium, americium, curium, berkelium and californium. There are five isotopes of plutonium but only two have commercial uses: P-238 and P-239. P-239 is what is used in nuclear weapons and to fuel nuclear power plants. With a half-life of about 24,000 years, this is some pretty nasty stuff. In 1945 and 1946, during research for the Manhattan Project, two scientists died and many others had their lives cut short in two separate incidents with the same plutonium core that briefly went critical: first because a researcher accidentally dropped a brick on it, and once when a researcher accidentally encased it in a neutron reflector. Due to these accidents, the core would become known infamously as the Demon Core. P-238 has a half life of only 88 years and is much less dangerous—its radioactivity is known as alpha decay, where it emits a helium ion instead of gamma or X-rays. This type of radiation is much easier to shield and since a kilogram of P-238 can generate over 500 watts of power for decades, it’s perfect as an onboard power plant for space probes: Viking, Galileo and Cassini to name a few. For a while in the 1970s, P-238 was used to power pacemakers for patients who did not want to risk repeated surgeries every time their battery wore out, and although pacemakers now use lithium-iodide batteries, there are still 50-100 people still living with functioning P-238 pacemakers.